Understanding Mass Transport and Reaction Environment to Optimize CO2 Electrodialysis Systems

Abstract Electrodialysis (ED) is a critical technology for decarbonization, which can be paired with direct air capture to produce a concentrated CO2 stream for efficient carbon utilization and storage. Although previous studies have significantly advanced CO2 ED at the process, membrane, and system levels, the coupled mass transport and reaction environment governing CO2 regeneration remain insufficiently understood, limiting further improvement in current efficiency. Here we develop a spatially resolved modeling framework for CO2 ED. Our approach captures the interplay among concentration polarization, pH gradient, and reaction localization, thereby enabling direct prediction of CO2 generation rate, proton utilization efficiency, and bubble nucleation barrier. Using three representative electrolytes with distinct acid–base properties, we show that buffering and acidity can substantially reshape ion distributions and reaction zones, which produce electrolyte-specific trade-offs between CO2 regeneration and bubble nucleation. Building on these mechanistic insights, we further identify ED cell geometries and operating conditions that maximize proton utilization efficiency while mitigating undesirable bubble nucleation. This work elucidates mass transport and reaction environment in CO2 ED, providing transport-informed design insights for efficient CO2 regeneration powered by renewable electricity.